trigger_error( ERROR_VALIDATE_FAILURE, ERROR );

//custom_functions_inc.php
     error_parameters( 'the original_due_date must > 1' );
         trigger_error( ERROR_VALIDATE_FAILURE, ERROR );

//custom_constants_inc.php
<?php
define( 'SENIOR_DEVELOPER', 60 );
define( 'ERROR_VALIDATE_FAILURE', 2000 );

//custom_strings_inc.php
<?php
#echo <<<'DOCN'
#<script type="text/javascript">
#alert("loading ... custom_strings_inc.php");
#</script>
#DOCN;
#$g_window_title = 'Wilson-Title';

switch( $g_active_language ) {
        case 'english':
                $s_current_test = 'CurrentTest';
                $MANTIS_ERROR[ERROR_VALIDATE_FAILURE] = 'error be made because %s'; 
                break;
        case 'chinese_simplified':
                $s_current_test = '当前时间测试';
                $MANTIS_ERROR[ERROR_VALIDATE_FAILURE] = '出错原因: %s'; 
                break;
        default:
                # Default language, as defined in config/config_inc.php
                # ($g_default_language, English in this case)
                $s_current_test = 'current_test';
                break;
}